This invention relates to hydraulic steering assemblies for outboard marine motors and, in particular, to steering systems for twin outboard motors.
Hydraulic steering systems for marine craft having outboard motors are well known and desirable accessories. Conventionally such steering systems have a steering wheel located remotely from the engine. A hydraulic pump is located on the steering wheel and is hydraulically connected to a steering assembly by hydraulic lines. A steering apparatus is mounted on the outboard propulsion unit, or one or more of the units in the case of marine craft having a plurality of outboard propulsion units, and includes a hydraulic cylinder with a piston rod which reciprocates and thus steers the propulsion unit about a steering axis. A tie-bar typically connects the steering apparatus to the second propulsion unit in the case of craft having twin propulsion units.
U.S. Pat. No. 4,373,920 to Hall et al., teaches that the traveling cylinder can be attached to the tiller arm by a slider mechanism wherein a lost motion connection is established between the tiller arm and the cylinder in order to compensate for the arcuate movement of the tiller arm. Alternatively, a drag link mechanism can be pivotally attached between one end of the cylinder and the tiller arm. These mechanisms have certain limitations discussed in U.S. Pat. No. 5,092,801 to McBeth.
McBeth discloses a connector which provides a strong and simple universal connection between the hydraulic steering assembly and the tiller arm of the engine. This eliminates a lost motion type slider. However, the mechanism requires significant rotation of the support brackets about the tilt axis of the motor. This rotation may be inhibited by such factors as poor maintenance, including the overtightening of nuts and other components or by corrosion, for example. If the support brackets are thus inhibited from rotating, then the steering action is impaired. This possibility has prevented widespread commercial acceptance of the McBeth steering assembly, even though it appears to provide significant advantages over the prior art.
Additional problems are encountered with hydraulic steering systems for twin outboard motors since the motors must be capable of tilting independently about the tilt axis. Conventionally tie-bars are connected to outer holes of the tillers or to plates attached to the tiller. Both systems take up considerable space, particularly the latter, with accompanying potential to interfere with other components such as transoms and splashwells. Also damage can result from excessive toe in of one or both motors when one of them is tilted up.
It is therefore an object of the invention to provide an improved hydraulic steering assembly for twin outboard motors which overcomes disadvantages associated with the prior art.
It is also an object of the invention to provide an improved hydraulic steering assembly for twin outboard motors which reduces significantly rotation of the support brackets about the tilt axis of the motor, thus allowing continued steering even when rotation of the brackets is impaired.
It is a further object of the invention to provide an improved steering assembly for twin outboard motors which reduces toe in (rotation of one or both motors about the steering axes) as one motor is tilted up.
It is a still further object of the invention to provide an improved hydraulic steering assembly for twin outboard motors which is simple and reliable in construction and is relatively easy to install and maintain.
According to one aspect of the invention there is provided a hydraulic steering assembly for applying a force to tillers of two or more marine outboard propulsion units and, accordingly rotating each propulsion unit about a steering axis about a steering axis between a center position and hard over positions to each side of the center position. The propulsion units are supported for arcuate movement about a tilt axis which is generally perpendicular to the steering axis. The steering assembly includes a hydraulic steering apparatus mounted on a first propulsion unit which includes a hydraulic cylinder pivotally connected to a member which is pivotally mounted on the tiller of the first propulsion unit. A tie-bar is pivotally connected to the steering apparatus and pivotally connected to the tiller arm of a second said propulsion unit.
According to another aspect of the invention, there is provided a hydraulic steering assembly for applying a force to tillers of two or more marine, outboard propulsion units and, accordingly, rotating each said propulsion unit about a steering axis between an center position and hard over positions to reach side of the center position, the propulsion units being supported for arcuate movement about a tilt axis which is generally perpendicular to the steering axis. The steering assembly comprises a hydraulic steering cylinder and an elongated piston rod reciprocatingly mounted within the cylinder for movement along a piston rod axis. A pair of support arms are pivotable about the tilt axis of a first propulsion unit and are connected to the piston rod. They allow arcuate movement of the rod about the tilt axis, while maintaining the rod parallel to the tilt axis. A member is pivotally mounted on the tiller of the first propulsion unit for pivoting about a first link axis which is parallel to the steering axis. A cylinder arm is connected to the cylinder and extends radially outwards from the piston rod axis. The cylinder arm is pivotally connected to the member for pivoting about a second link axis which is parallel to the piston rod axis. The cylinder arm moves through a rotational position, when the first propulsion rotates from the center position to either hard over position. The second link axis and the rod axis are on a plane parallel to the steering axis of the first propulsion unit. A tie bar is pivotally connected to the member and to a second said propulsion unit.